Here’s a larger slice of Thursday’s mystery image. Small moons perturb Saturn’s F Ring, as explained on the Cassini site here. The NASA scientists explain:

For some time, scientists have suspected the presence of tiny moonlets that orbit Saturn in association with the clumpy ring. As the small satellites move close to the F ring core they leave a gravitational signature. In some cases they can draw out material in the form of a “streamer”–a miniature version of the interaction Cassini has witnessed between Prometheus and the F ring material. The dynamics of this interaction are the same, but the scale is different. See Thieving Moon for a view of Prometheus creating a streamer.

Scientists speculate that there could be several small moons with a variety of sizes involved in the creation of structures like the one seen here.